Two polaroids with their principal sections aligned at `60^@`, are placed in the path of a beam of unpolarized light of intensity `I_0`. What is the intensity of light transmitted ?

Explanation

Intensity of emergent light from the first polaroid
`I_1=(I_0//2)`
Light of intensity `(I_0//2)` falls on the second polaroid with its principal section at`60^@`
`therefore` Intensity of light trnasmitted
`I_2=I_1 cos^2 theta`
`I_0/2cos^2 60^@=I_0/2(1/4)=I_0/8`
Result: The intensity of light transmitted =`I_0/8`